1. Field of the Invention
The present invention relates to a gas sensor element and a gas sensor.
2. Description of the Related Art
To date, gas sensors including sensor elements for detecting the concentrations of predetermined gases, e.g., NOx, in gases to be measured, such as automobile exhaust gases, are known. It is also known that a porous protective layer is formed on the surface of the sensor element in such a gas sensor. For example, PTLs 1 and 2 describe a technique to form the porous protective layer by causing heat-resistant particles, e.g., alumina, to adhere to the surface of a sensor element by plasma spraying. It is mentioned that, for example, cracking or the like of the sensor element due to adhesion of moisture in a gas to be measured can be suppressed by formation of the porous protective layer.